Project Abstract Racial disparities in cancer treatment may contribute to racial mortality disparities. The Institute of Medicine report, Unequal Treatment, and other research suggests that the quality of patient-physician communication during racially discordant (Black patient, non-Black physician) clinical interactions, which constitute about 80% of Black patients' clinical interactions, likely contributes to treatment disparities. Prior research, including our own, finds that these interactions are less positive and productive than racially concordant interactions; and patient and physician racial attitudes (e.g., patient suspicion of medical care Blacks receive; physician implicit racial bias) affect the quality of communication during interactions. Such racial attitudes are largely expressed through subtle nonverbal behaviors; however, prior research has not focused on these behaviors or examined the dynamic, reciprocal way they are expressed. This project will do this by examining nonverbal synchrony, or the coordination of physical movement; which research shows reflects pre-interaction attitudes and predicts participants' post-interaction perceptions of each other and affect toward one another. Thus, we will investigate nonverbal synchrony in both racially concordant and racially discordant interactions as a means to better understand racial disparities in clinical communication. Data will include: racially concordant (n = 163) and racially discordant (n = 68) video-recorded oncology interactions, patient and oncologist self-reported racial attitudes, post-visit perceptions of the interaction and of each other, as well as observer ratings of physician's patient-centered communication, and patient and physician affect and rapport. Aim 1 is to assess and compare nonverbal synchrony between physicians and patients in racially concordant and racially discordant oncology interactions using innovative software and analytical methods that capture the subtle and reciprocal nature of this channel of communication. Aim 2 is to determine the relative influence of nonverbal synchrony on patient and physician affect and communication displayed in racially concordant and racially discordant oncology interactions. Aim 3 is to examine causes and consequences of nonverbal synchrony in racially discordant oncology interactions. Aim 4 is to develop and test a model that links physician and patient racial attitudes to nonverbal synchrony and, in turn, interaction outcomes. This study is significant because findings will improve knowledge of 1) differences in nonverbal communication in racially concordant and racially discordant oncology interactions, 2) how racial attitudes are communicated during oncology interactions, 3) how this communication affects interaction outcomes, and 4) how subtle nonverbal communication contributes to treatment disparities. This knowledge provides information about communication in racially discordant interactions that can be used in medical education and evaluations of treatment disparity interventions. The study is innovative because it examines an unexplored channel of communication affecting interaction outcomes, using innovative methods to assess dynamic, reciprocal patient-physician communication.